Core network node and method for handling redundant URLLC connections

ABSTRACT

The current disclosure proposes URLLC support indication exchange between the network nodes and URLLC support by the network indication in the Registration procedure so that a URLLC capable UE knows whether it could initiate URLLC type of PDU session establishment.

This application is a National Stage Entry of PCT/JP2019/047749 filed onDec. 6, 2020, which claims priority from European Patent Application19150842.3 filed on Jan. 8, 2019, the contents of all of which areincorporated herein by reference, in their entirety.

TECHNICAL FIELD

The present disclosure relates to a communication system. The disclosurehas particular but not exclusive relevance to wireless communicationsystems and devices thereof operating according to the 3rd GenerationPartnership Project (3GPP) standards or equivalents or derivativesthereof. The disclosure has particular although not exclusive relevanceto the provision of Ultra Reliable and Low Latency Communication (URLLC)in the so-called ‘5G’ (or ‘Next Generation’) systems.

BACKGROUND ART

The 3GPP SA2 Working Group is working on URLLC (Ultra Reliable LowLatency Communication) Study Item. The objective is to study and performan evaluation of potential architecture enhancements for supportingURLLC services in the 5G System. Specifically, the following aspects arecovered:

-   -   Investigate the key issues for meeting the URLLC requirements on        latency, jitter and reliability in 5G System as defined in TS        22.261    -   Study how to minimize the impacts of the UE mobility to the        latency and jitter between the Access Network (AN) and the Core        Network (CN), and within the CN.    -   Study how to realize transmission with reliability higher than        the reliabilities of a single user plane tunnel of N3 and N9 and        NFs in the user plane path.    -   Study how to monitor the QoS of the QoS flow with URLLC        requirement.    -   Study potential impacts to charging and policy control

The SA2 have defined a solution (TR 23.725, 6.1) which enables aterminal device to set up two redundant PDU sessions over the 5G network(see FIG. 1 ) so that the network will attempt to make the paths of thetwo redundant PDU sessions independent whenever that is possible. The3GPP network provides two paths from the device: the first PDU sessionspans from the UE via the NG-RAN node1 501 to the UPF1 751 acting as thePDU session Anchor, and the second PDU session spans from the UE via theNG-RAN node2 502 to the UPF2 752 acting as the PDU session Anchor. Basedon these two independent PDU sessions, two independent paths are set up.This solution is based on the Dual Connectivity feature that issupported both by LTE and NR. The UE sets up two PDU sessions, one viathe MNG-RAN node 501 to the UPF1 751 acting as the PDU session anchor,and another one via the SNG-RAN node 502 to the UPF2 752 acting as thePDU session anchor. The UPF1 751 and the UPF2 752 connect to the sameData Network (DN), even though the traffic via the UPF1 751 and the UPF2752 might be routed via different user plane nodes within the DN. TheUPF1 751 and the UPF2 752 are controlled by the SMF1 731 and the SMF2732, respectively, where the SMF1 731 and the SMF2 732 may coincidedepending on operator configuration of the SMF selection. It is reliedon upper layer protocols, such as the IEEE TSN (Time SensitiveNetworking) FRER (Frame Replication and Elimination for Reliability), tomanage the replication and elimination of redundant packets/frames overthe duplicate paths.

SUMMARY OF INVENTION Technical Problem

The above described URLLC solution TR23.725, 6.1 and other URLLCsolutions make assumptions that there will be deployment compatibilitybetween the RAN nodes the Core Network Nodes like:

-   -   The core network UPF deployment is aligned with RAN deployment        and supports redundant user plane paths.    -   The underlying transport topology is aligned with the RAN and        UPF deployment and supports redundant user plane paths.    -   The physical network topology and geographical distribution of        functions also supports the redundant user plane paths to the        extent deemed necessary by the operator.

These assumptions however would be difficult or even impossible to bemet by the operators in order to assure that a UE that requests aredundant user path (i.e., URLLC user connection) will always connect toRAN and Core Network nodes that support URLLC (i.e., support user patchredundancy), see FIG. 1 .

There is no guarantee that:

-   -   [problem 1] A URLLC capable UE will select a URLLC supporting        NG-RAN—Currently the UE does not know which NG-RAN is the URLLC        supporting NG-RAN.    -   [problem 2] A URLLC capable NG-RAN will select a URLLC capable        AMF—Currently the NG-RAN does not have information about which        AMFs in the AMF sets the NG-RAN is connected to, are the URLLC        supporting AMF. It is not practical (i.e., not cost effective)        that all connected AMFs would be supporting URLLC.    -   [problem 3] A URLLC capable AMF will select URLLC capable        SMF—Currently the AMF does not have information about which SMF        is the URLLC supporting SMF. It is not practical (i.e., not cost        effective) that all SMFs that an AMF can select are the URLLC        supporting SMFs.

Solution to Problem

According to an aspect of the present disclosure, a core network nodeincludes: means for receiving a request for establishment of a ProtocolData Unit, PDU, session; means for determining that redundant handlingis not allowed for the PDU session; and means for performing rejectingthe establishment of the PDU session with redundancy handling.

According to another aspect of the present disclosure, a method for acore network node, includes: receiving a request for establishment of aProtocol Data Unit, PDU, session; determining that redundant handling isnot allowed for the PDU session; performing rejecting the establishmentof the PDU session with redundancy handling.

Advantageous Effects of Invention

In certain aspects, the core network node, the method for the corenetwork node may provide a technology for managing redundant handling ofthe PDU session(s).

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an example of URLLC via redundant user plane paths.

FIG. 2 illustrates an example of the URLLC support indication by thenetwork in the UE Registration procedure.

FIG. 3 illustrates an example of UE network capability informationelement.

FIG. 4 illustrates schematically a first example of the URLLC supportindication exchange between the AMF and the NG-RAN during the NGConnection Setup procedure.

FIG. 5 illustrates schematically a second example of the URLLC supportindication exchange between the AMF and the NG-RAN during the RANConfiguration Update procedure.

FIG. 6 illustrates schematically a third example of the URLLC supportindication exchange between the AMF and the NG-RAN during the AMFConfiguration Update procedure.

FIG. 7 illustrates an example of the URLLC support indication broadcastin the system information.

FIG. 8 illustrates an example of the URLLC supporting SMF selection.

FIG. 9 schematically illustrates a mobile telecommunication system.

FIG. 10 is a block diagram illustrating the main components of the UE.

FIG. 11 is a block diagram illustrating the main components of anexemplary (R)AN node 5.

FIG. 12 is a block diagram illustrating the main components of a genericcore network node.

DESCRIPTION OF EMBODIMENTS

In order to avoid URLLC connections establishment (e.g., user redundancypath establishment) failures, the following aspects are provided:

-   -   1) The URLLC support indication by the network during the UE        Registration so that the UE 3 requests for user path redundancy        only when the network supports URLLC. This aspect resolves the        problem 1, 2 and 3.    -   2) The URLLC support negotiation between the AMF 710 and the        NG-RAN node 5. This aspect resolves the problem 2.    -   3) The NG-RAN node 5 broadcasts an URLLC support indication.        This aspect addresses the problem 1.    -   4) The URLLC supporting SMF selection. This aspect resolves the        problem 3.    -   5) The URLLC support via the designated network slice. This        aspect resolves the problems 1, 2 and 3 in case the network        supports the URLLC homogeneously in the whole registration area.

Aspect 1—URLLC Support Indication by the Network During UE Registration

The Aspect 1 provides for a URLLC support indication by the networkduring the UE Registration procedure. This allows for the UE 3 torequest for URLLC (e.g., PDU Session establishment with user pathredundancy) only when the network supports URLLC. An exemplary procedureof the URLLC support indication by the network is illustratedschematically in the FIG. 2 .

1) A URLLC capable UE 3 initiates a registration procedure with thenetwork by triggering the Registration Request message. If the UE 3 iscapable of URLLC (e.g., user plane redundancy), the UE 3 indicates itscapability/support for URLLC by adding a URLLC capability indicationparameter (or any other indication for the purpose of indicating thecapability of the UE 3 to support the PDU Session establishment withuser plane redundancy called for shorter URLLC) in the RegistrationRequest message. The URLLC capability/support parameter can be adesignated parameter within the Registration Request message or a partof the UE network capability information element, see FIG. 3 .

The Registration Request message is included (e.g., in the form of NASPDU, container or message) in an RRC message (e.g., RRC ConnectionRequest message or RRC Connection Complete message or any other ASmessage). The UE 3 may also include its capability/support indicationfor URLLC support in the RRC message itself as a designated parameter oras a part of the UE Capability Information element. The URLLCcapability/support indication in the RRC message will help the NG-RANnode 5 to select an URLLC supporting AMF in case not all connected AMFssupport URLLC.

2) The NG-RAN node 5 selects an AMF 710. If the RRC message from the UE3 includes indication for URLLC support/capability, the NG-RAN node 5selects an AMF 710 that supports URLLC. The NG-RAN node 5 may select anAMF 710 based on a combination of the indication for URLLCsupport/capability and an NSSAI (a list of S-NSSAIs) in the RRC message.The NG-RAN node 5 forwards the Registration Request message from the UE3 to the selected AMF 710 within the N2 Setup Request message.

3) The AMF 710 may enquire with the UDM/UDR 720 via the Nudm_SDM_Getprocedure or any other procedure for retrieving UE subscriptioninformation from the UDM/UDR 720, in case URLLC support is thesubscription based service. The UE subscription for URLLC is subscriberdata information stored in the UDM/UDR 720. This information indicateswhether the UE 3 is allowed to establish URLLC including the redundantuser plane path establishment. This indication can be per UE basis orper PDU session basis or per Subscribed S-NSSAI basis. The AMF 710 mayget a URLLC capability/support indication from the PCF.

4) If the network supports URLLC, the AMF 710 indicates URLLC support tothe UE 3. If the URLLC support is subscription based service, the AMF710 verifies UE's subscription for the URLLC before indication of URLLCsupport to the UE 3.

The AMF 710 may also consider operator policy or configuration beforeindicating the support for URLLC. For example, if none of the SMFsconnected to the AMF 710 support the URLLC feature, then the AMF 710shall indicate URLLC not supported to the UE 3.

Unless all conditions are met, the AMF 710 indicates URLLC notsupported.

5) The AMF 710 indicates the URLLC support to the UE 3 within theRegistration Accept message. The AMF 710 may include a URLLC supportparameter in the Registration Accept message. The AMF 710 may include aURLLC support parameter per allowed S-NSSAI basis. The AMF 710 mayinclude a URLLC cause parameter that is associated with the URLLCsupport parameter. The URLLC support parameter may indicate:

-   -   URLLC support=URLLC supported; or        -   URLLC rejected; or        -   URLLC not supported; or        -   URLLC not subscribed; or        -   URLLC not supported in this location; and/or        -   URLLC not supported by the vPLMN.

The AMF 710 may also indicate the support for URLLC within the UEConfiguration Update message, especially if the support for URLLCchanges while the UE 3 is still in the same registration area. The AMF710 may include a URLLC support parameter per allowed S-NSSAI basis.

The AMF 710 transmits the Registration Accept message to the UE 3 viathe NG-RAN node 5 within the N2 Setup Response message. The AMF 710 mayalso include the URLLC support indication within the N2 Setup Responsemessage itself. This way the AMF 710 configures or updates the NG-RANnode 5 with the AMF capability for URLLC support. The NG-RAN node 5 usesthe AMF capability for URLLC support when selecting an AMF for the newlyregistering UEs with capability for URLLC, e.g., to select the URLLCcapable AMF for URLLC capable UEs.

6) The NG-RAN node 5 delivers the UE Registration Accept message to theUE 3 in an RRC message.

7) Based on the URLLC support indication, the UE 3 performs theappropriate PDU session establishment procedure. If the URLLC supportindication is included in the Registration Accept message and:

-   -   a) URLLC support indication=URLLC supported—The URLLC is        supported by the network and the UE 3 can initiate URLLC        connection (e.g., PDU Session establishment with user plane        redundancy) when needed.    -   b) URLLC support indication=URLLC rejected—this means that the        network in general supports URLLC but the use of it is rejected        for some reason. In this case the AMF 710 may include a URLLC        cause parameter as well in the Registration Accept message to        indicate the reason for the URLLC rejection. Examples for the        rejection cause could be the following use cases:    -   temporary not supported;    -   network overloaded.    -   c) URLLC support indication=URLLC not supported—The URLLC is not        supported by the network in general. The UE 3 shall not trigger        the request for URLLC while in this PLMN.    -   d) URLLC support indication=URLLC not subscribed—The UE 3 has no        subscription for URLLC. The AMF 710 may also include the URLLC        cause parameter in order to indicate whether the subscription        restriction is per UE in general or per PDU session or per        S-NSSAI. The UE 3 shall not trigger the request for URLLC while        with this PLMN. If there is a cause clarifying the subscription        restriction, the UE 3 shall follow the subscription restrictions        e.g., not to initiate URLLC for a specific PDU session or        S-NSSAI.    -   e) URLLC support indication=URLLC not supported in this        location—The network does not support URLLC in this location,        e.g., in this cell or TA or Registration Area. The UE 3 shall        not initiate the request for URLLC support while the UE 3 is in        that location area, e.g., cell or TA or Registration Area.    -   f) URLLC support indication=URLLC not supported by the vPLMN—The        URLLC is not supported by the visited PLMN. The UE 3 shall not        trigger the request for URLLC while in that vPLMN.

Lack of the URLLC support indication can be interpreted by the UE 3 asif URLLC is not supported.

The URLLC support indication that is indicated by the network may be anindication of support one or a combination of ones listed below:

-   -   IEEE 802.1CB (FRER) [8]    -   IEEE 802.1Q [9]    -   Dual Connectivity

The URLLC capability indication parameter that is indicated by the UE 3may be an indication of support one or a combination of ones listedbelow:

-   -   IEEE 802.1CB (FRER) [8]    -   IEEE 802.1Q [9]    -   Dual Connectivity

Aspect 2—the URLLC Support Negotiation Between the AMF 710 and theNG-RAN Node 5

The Aspect 2 is about the URLLC capability exchange between the AMF 710and the NG-RAN node 5. The NG-RAN node 5 needs to know which of theconnected AMFs are URLLC capable so that the NG-RAN node 5 can select anURLLC supporting AMF for UEs that are URLLC capable.

Example 1. FIG. 4 illustrates schematically a first example of the URLLCsupport indication exchange (i.e., URLLC capability exchange) betweenthe AMF 710 and the NG-RAN node 5 during the NG Connection Setupprocedure.

1) When the NG-RAN node 5 initiates connection setup with one of theconnected AMFs, the NG-RAN node 5 indicates in the NG Setup Requestmessage its capability for URLLC support.

2) The AMF 710 indicates its capability for URLLC support in the NGSetup Response message by including a URLLC support indicationparameter. This way the AMF 710 configures or updates the NG-RAN node 5with information on its capability for URLLC support. NG-RAN node 5saves this information (i.e., the URLLC support indication parameter forthe AMF 710) and the NG-RAN node 5 uses this information for AMFselection for new UE entrants, i.e., when a URLLC capable UE registersor re-registers with the network, the NG-RAN node 5 will select a URLLCsupporting AMF 710. The lack of the URLLC support indication parametercan be interpreted by the NG-RAN node 5 as if the AMF 710 does notsupport URLLC.

The AMF 710 may also consider the operator policy or the configurationto set the URLLC support indication parameter. For example, if none ofthe SMFs connected to the AMF 710 support the URLLC feature, then theAMF 710 shall indicate URLLC not supported to the NG-RAN node 5. The AMF710 may set the URLLC support indication parameter per S-NSSAI basis.

Example 2. FIG. 5 illustrates schematically a second example of theURLLC support indication exchange (i.e., URLLC capability exchange)between the AMF 710 and the NG-RAN node 5 during the RAN ConfigurationUpdate procedure.

1) When the NG-RAN node 5 initiates the RAN Configuration updateprocedure to an AMF 710, the NG-RAN node 5 indicates in the RANConfiguration Update message its capability for URLLC support.

2) The AMF 710 indicates its capability for URLLC support in the RANConfiguration Update Acknowledge message by including a URLLC supportindication parameter. This way the AMF 710 configures or updates theNG-RAN node 5 with information on its capability for URLLC support. TheNG-RAN node 5 saves this information (i.e., the URLLC support indicationparameter for the AMF 710) and the NG-RAN node 5 uses this informationfor the AMF selection for new UE entrants, i.e., when a URLLC capable UEregisters or re-registers with the network, the NG-RAN node 5 willselect a URLLC supporting AMF 710. The lack of the URLLC supportindication parameter can be interpreted by the NG-RAN node 5 as the AMF710 does not support URLLC.

The AMF 710 may also consider operator policy or configuration to setthe URLLC support indication parameter. For example, if none of the SMFsconnected to the AMF 710 support the URLLC feature, then the AMF 710shall indicate URLLC not supported to the NG-RAN node 5. The AMF 710 mayset the URLLC support indication parameter per S-NSSAI basis.

Example 3. FIG. 6 illustrates schematically a third example of the URLLCsupport indication exchange (i.e., URLLC capability exchange) betweenthe AMF 710 and the NG-RAN node 5 during the AMF Configuration Updateprocedure.

1) When the AMF 710 initiates the AMF Configuration update procedure toan NG-RAN node 5, the AMF 710 indicates in the AMF Configuration Updatemessage its capability for URLLC support. This way the AMF 710configures or updates the NG-RAN node 5 with information about itscapability for URLLC support. The NG-RAN node 5 saves this information(i.e., the URLLC support indication parameter for the AMF 710) and theNG-RAN node 5 uses this information for the AMF selection for new UEentrants, i.e., when a URLLC capable UE registers or re-registers withthe network, the NG-RAN node 5 will select a URLLC supporting AMF 710.The lack of URLLC support indication can be interpreted by the NG-RANnode 5 as the AMF 710 does not support URLLC.

The AMF 710 may also consider operator policy or configuration to setthe URLLC support indication parameter. For example, if none of the SMFsconnected to the AMF 710 support the URLLC feature, then the AMF 710shall indicate URLLC not supported to the NG-RAN node 5. The AMF 710 mayset the URLLC support indication parameter per S-NSSAI basis.

2) The NG-RAN node 5 indicates its capability for URLLC support in theAMF Configuration Update Acknowledge message by including a URLLCsupport indication parameter.

Aspect 3—NG-RAN Node 5 Broadcasts an URLLC Support Indication

The Aspect 3 proposes an URLLC support/capability broadcast by theNG-RAN node 5, i.e., a URLLC supporting indication parameter in one ofthe System Information messages to be broadcast by the NG-RAN node 5.This is an indication for the UEs that URLLC is supported by the networkin that cell. The main steps of the Aspect 3 are illustratedschematically in FIG. 7 .

1) Preamble—The AMF 710 has already configured or updated the NG-RANnode 5 with information on whether the Core Network support URLLC. Thesupport for URLLC by the Core Network can change with location, time orbased on the overload conditions. Any changes of the URLLC support bythe Core Network is updated in the NG-RAN node 5 during the NG Setupprocedure or the RAN Configuration Update procedure or the AMFConfiguration Update procedure. The AMF 710 may indicate a URLLC supportper S-NSSAI basis.

2) If the AMF 710 has indicated the core network's support for URLLC andthe NG-RAN node 5 itself also supports URLLC, the NG-RAN node 5 maybroadcast the URLLC support indication parameter in one of the Systeminformation in order to indicate to the UEs that the URLLC is supportedin that cell. The NG-RAN node 5 may broadcast the URLLC supportindication parameter per slice basis or per DNN basis.

3) If the URLLC support indication parameter is present in the SystemInformation broadcast, the UE 3 is aware that it can register for URLLCand also can trigger the URLLC PDU session establishment when needed.

Aspect 4—URLLC Supporting SMF Selection

The Aspect 4 proposes a method for the URLLC supporting SMF selection bythe AMF 710. When a PDU session establishment request is initiated fromthe URLLC capable UE or the PDU session request includes the RSN(Redundancy Sequence Number), the AMF 710 needs to select an SMF 730that supports URLLC. The AMF 710 performs the NRF discovery by includingthe URLLC parameter in the Nnrf Discovery Request. This way the AMF 710selects a URLLC supporting SMF 730, see FIG. 8 .

1) A URLLC capable UE has already registered with the URLLC supportingAMF 710.

2) A UE 3 initiate the PDU session establishment for URLLC (e.g., forthe redundant user path with the Redundant Sequence Number).

3) The AMF 710 queries the appropriate NRF 740 in the serving PLMN byissuing the Nnrf_NFDiscovery_Request including an URLLC indication alongwith the other necessary parameter for the SMF selection.

4) The NRF 740 uses the URLLC indication by the AMF 710 as a serviceparameter to find an URLLC supporting SMF 730. If an URLLC supportingSMF 730 is available, the procedure continues with step 5 to step 8. Ifthe URLLC supporting SMF 730 is not available, the procedure continuesfrom step 9.

5) The NRF 740 in the serving PLMN provides to the AMF 710, e.g.,FQDN(s) or IP address(s), of a set of the discovered SMF instance(s)(e.g., the SMF1 731) or Endpoint Address(es) of SMF service instance(s)that support URLLC in the Nnrf_NFDiscovery_Request response message. Ifthe NRF 740 cannot find any SMFs that support the URLLC feature, thenthe NRF 740 replies to the AMF 710 with null or the error indication. Inthis case, the AMF 710 may restart from the step 3 without the URLLCindication included in the Nnrf_NFDiscovery_Request message in order tofind a non URLLC supporting SMF 730, i.e., the normal SMF 730.

6) The AMF 710 invokes the Nsmf_PDUSession_CreateSMContext serviceoperation.

7) If the SMF1 731 accepts the PDU session request, the SMF1 731responds with the Nsmf_PDUSession_CreateSMContext Response message.

8) The AMF 710 responds with the PDU Session Establishment Acceptmessage. The AMF 710 may include the URLLC SM cause parameter (or anyother notation for a parameter with the purpose of indicating the statusof the URLLC support) in the PDU Session Establishment Accept message.The URLLC SM cause parameter may indicate (i.e., it can take) thefollowing values:

-   -   URLLC configured/supported—i.e., setting the URLLC PDU session        is successful;    -   URLLC not configured/supported—i.e., URLLC PDU session        establishment is not possible (e.g., there is no URLLC        supporting SMF 730 available in the set of the SMFs that the AMF        710 can choose from). In this case the UE 3 shall not initiate        another PDU session request for URLLC in the current        registration area. This URLLC SM cause indication may be        interpreted by the UE 3 as if the PDU session has been        established without URLLC configuration; or    -   URLLC not configured/supported in this location—the URLLC is not        supported in the current location, e.g., cell, TA or        registration area. In this case the UE 3 shall not initiate        another PDU session request for URLLC PDU session establishment        in this location area, e.g., cell or TA or registration area.        This URLLC SM cause indication may be interpreted by the UE 3 as        if the PDU session has been established without the URLLC        configuration; and/or    -   URLLC not configured/supported by the vPLMN—the URLLC is not        supported by the visited PLMN. In this case the UE 3 shall not        initiate another PDU session request for URLLC in this vPLMN.        This URLLC SM cause indication may be interpreted by the UE 3 as        if the PDU session has been established without the URLLC        configuration; and/or    -   URLLC overloaded—i.e., core network is overloaded (e.g., there        is an URLLC supporting SMF 730 within the set of SMFs that the        AMF 710 can choose from but that URLLC SMF is not available for        overload reasons). In this case the AMF 710 may also return an        URLLC back-off timer. If the URLLC back-off timer is included,        the UE 3 shall not initiate another URLLC PDU Session        establishment until the expiry of the URLLC back-off timer. This        URLLC SM cause indication may be interpreted by the UE 3 as if        the PDU session has been established without the URLLC        configuration; and/or    -   URLLC temporary unavailable—any technical failure or other        reason that makes the URLLC unavailable. In this case the AMF        710 may also return an URLLC back-off timer. If URLLC back-off        timer is included, the UE 3 shall not initiate another URLLC PDU        Session establishment until the expiry of the URLLC back-off        timer. This URLLC SM cause indication may be interpreted by the        UE 3 as if the PDU session has been established without the        URLLC configuration.

Lack of URLLC SM cause parameter can be interpreted by the UE 3 as ifthe PDU session has been established with the URLLC configuration.

Lack of URLLC SM cause parameter can be interpreted by the UE 3 as ifthe PDU session has been established without the URLLC configuration.

9) When the NRF 740 cannot find a URLLC supporting SMF 730, the NRF 740responds to the AMF 710 with SMF_cause parameter in theNnrf_NFDiscovery_Response(SMF_cause) message. The SMF cause may indicatethe reason for SMF rejection, e.g.:

-   -   URLLC SMF not available/not supported—i.e., there is no URLLC        supporting SMF 730 available in the set of SMFs that the AMF 710        can choose for;    -   URLLC supporting SMF overloaded—i.e., there is an URLLC        supporting SMF 730 within the set of SMFs that the AMF 710 can        choose from but that URLLC SMF is not available for overload        reasons.    -   URLLC supporting SMF temporary unavailable—any technical or        other reason that makes the URLLC SMF unavailable.

10) The AMF 710 rejects the PDU Session establishment by sending the PDUSession Establishment Reject message. The AMF 710 may include a URLLC SMcause in the PDU Session Establishment Reject message and, in somecases, a URLLC back-off timer to indicate, e.g.:

-   -   URLLC not configured/supported—i.e., the URLLC PDU session        establishment is not possible (e.g., there is no URLLC        supporting SMF 730 available in the set of SMFs that the AMF 710        can choose from). In this case the UE 3 shall not initiate        another PDU session request for URLLC in the current        registration area.    -   URLLC not configured/supported in this location—the URLLC is not        supported in the current location, e.g., cell, TA or        registration area. In this case the UE 3 shall not initiate        another PDU session request for URLLC PDU session establishment        in this location area, e.g., cell or TA or registration area.    -   URLLC not configured/supported by the vPLMN—the URLLC is not        supported by the visited PLMN. In this case the UE 3 shall not        initiate another PDU session request for URLLC in this vPLMN.    -   URLLC overloaded—i.e., core network is overloaded (e.g., there        is an URLLC supporting SMF 730 within the set of SMFs that the        AMF 710 can choose from but that URLLC SMF is not available for        overload reasons). In this case the AMF 710 may also return an        URLLC back-off timer. If URLLC back-off timer is included, the        UE 3 shall not initiate another URLLC PDU Session establishment        until the expiry of the URLLC back-off timer.    -   URLLC temporary unavailable—any technical failure or other        reason that makes the URLLC unavailable. In this case the AMF        710 may also return an URLLC back-off timer. If the URLLC        back-off timer is included, the UE 3 shall not initiate another        URLLC PDU Session establishment until the expiry of the URLLC        back-off timer.

Lack of URLLC SM cause indication can be interpreted by the UE 3 as ifthe PDU session has been established without the URLLC configuration.

Aspect 5—URLLC Support Via Designated Network Slice

The Aspect 5 proposes the URLLC support attribution to be a built-innetwork slice attribute.

An S-NSSAI is comprised of:

-   -   A Slice/Service type (SST), which refers to the expected Network        Slice behaviour in terms of features and services;

A Slice Differentiator (SD), which is optional information thatcomplements the Slice/Service type(s) to differentiate amongst multipleNetwork Slices of the same Slice/Service type

Example 1: Proposes a new Slice Service Type (SST) value for URLLCsupport with redundant user plane path—URLLC redundant path or any othernotation for SST for the purpose of establishing PDU session with userplane redundancy, see Table 1.

Although Table 1 shows that value ‘4’ is used for URLLC support with theredundant user plane path, the SST value may take any other value forthe same purpose of URLLC support with the redundant user plane pathindication. When the AMF 710 provides the Allowed NSSAI (a list ofallowed S-NSSAIs) to the UE 3, the AMF 710 may include an S-NSSAIdesignated for the URLLC redundant path although the URLLC featurecannot be supported by the NG-RAN node 5 or 5GC. In this case, the AMF710 may indicate to the UE 3 that the redundant user path cannot beconfigured. When the AMF 710 provides the Allowed NSSAI (the list ofallowed S-NSSAIs) to the UE 3, the AMF 710 may not include an S-NSSAIdesignated for the URLLC redundant user path if the URLLC feature cannotbe supported by the NG-RAN node 5 or 5GC. In this case, the AMF 710 mayindicate the UE 3 that the non redundant path can still be configurablefor that 5-NSSAI.

TABLE 1 New standardised SST value of URLLC redundant path SSTSlice/Service type value Characteristics. eMBB 1 Slice suitable for thehandling of 5G enhanced Mobile Broadband. URLLC 2 Slice suitable for thehandling of ultra- reliable low latency communications. MIoT 3 Slicesuitable for the handling of massive IoT. URLLC redundant 4 URLLC withredundant user plane path path

Example 2: Proposes new Slice Differentiator (SD) for URLLC. The new SDincludes information whether the network slice support redundant userpath establishment.

When the AMF 710 provides the Allowed NSSAI (a list of allowed S-NSSAIs)to the UE 3, the AMF 710 may include an S-NSSAI designated for the URLLCredundant path although the URLLC feature cannot be supported by theNG-RAN node 5 or 5GC. In this case, the AMF 710 may indicate to the UE 3that the redundant user path cannot be configured.

When the AMF 710 provides the Allowed NSSAI (the list of allowedS-NSSAIs) to the UE 3, the AMF 710 may not include an S-NSSAI designatedfor the URLLC redundant user path if the URLLC feature cannot besupported by the NG-RAN node 5 or 5GC. In this case, the AMF 710 mayindicate the UE 3 that the non redundant path can still be configurablefor that S-NSSAI.

Beneficially, the above described aspects include, although they are notlimited to, one or more of the following functionalities:

-   -   1. URLLC Support negotiation among network nodes and URLLC        support indication by the network within the Registration        procedure or via the System Information broadcast so that a        URLLC capable UE is aware of whether it can trigger URLLC type        PDU Session establishment and avoid PDU Session establishment        for URLLC failure in case the URLLC is not supported by the        network.    -   2. URLLC supporting SMF selection by the AMF 710 by adding a new        URLLC parameter in the NRF enquiry procedure and return of URLLC        SM cause and URLLC back-off timer to the UE 3 in case of URLLC        PDU session establishment failure.

The above functionalities may be implemented using one or more of thefollowing exemplary features:

-   -   1) UE capability for URLLC indication in the RRC message    -   2) UE capability for URLLC indication in the Registration        Request message    -   3) Network support for URLLC indication in the Registration        Accept and UE Configuration Update messages.    -   4) Network support for URLLC indication in the System        Information broadcast.    -   5) AMF 710 support for URLLC indication in the N2 Setup Response        message, AMF 710 Configuration Update message and in RAN        Configuration Update Acknowledge message.    -   6) URLLC SM cause and URLLC back-off timer from the NRF 740 and        AMF 710 for the UE    -   7) URLLC support as a UE subscription information.    -   8) URLLC supporting SST and SD values for the Network Slice.

The above aspects describe exemplary methods comprising (at least someof) the following steps.

Aspect 1:

-   -   1) UE capability for URLLC indication in the RRC message    -   2) UE capability for URLLC indication in the Registration        Request message    -   3) URLLC support as a UE subscription information.    -   4) AMF 710 support for URLLC indication in the N2 Setup Response        message,    -   5) Network support for URLLC indication in the Registration        Accept and UE Configuration Update messages.

Aspect 2:

URLLC support information exchange between the AMF 710 and NG-RAN node 5

Aspect 3:

URLLC support by the network broadcast in the System Information.

Aspect 4:

URLLC supporting SMF selection by the AMF 710 via NRF enquiry.

Aspect 5:

URLLC supporting SST and SD values for the Network Slice.

Benefits

The disclosure proposes URLLC support indication by the network duringthe registration procedure so that a URLLC capable UE can avoid URLLCPDU session establishment failures when the network does not supportURLLC.

System Overview

FIG. 9 schematically illustrates a mobile (cellular or wireless)telecommunication system 1 to which the above aspects and examples areapplicable.

In this network, users of mobile devices 3 (UEs) can communicate witheach other and other users via respective base stations 5 and a corenetwork 7 using an appropriate 3GPP radio access technology (RAT), forexample, an E-UTRA and/or 5G RAT. It will be appreciated that a numberof base stations 5 form a (radio) access network or (R)AN. As thoseskilled in the art will appreciate, whilst one mobile device 3 and onebase station 5 are shown in FIG. 9 for illustration purposes, thesystem, when implemented, will typically include other base stations andmobile devices (UEs).

Each base station 5 controls one or more associated cells (eitherdirectly or via other nodes such as home base stations, relays, remoteradio heads, distributed units, and/or the like). A base station 5 thatsupports E-UTRA/4G protocols may be referred to as an ‘eNB’ and a basestation 5 that supports NextGeneration/5G protocols may be referred toas a ‘gNB’. In this example, the base station 5 forms part of a ‘NextGeneration’ RAN (NG-RAN) which supports 5G communications. It will beappreciated that some base stations 5 may be configured to support both4G and 5G, and/or any other 3GPP or non-3GPP communication protocols.

The mobile device 3 and its serving base station 5 are connected via anappropriate air interface (for example the so-called ‘Uu’ interfaceand/or the like). Neighbouring base stations 5 are connected to eachother via an appropriate base station to base station interface (such asthe so-called ‘X2’ interface, ‘Xn’ interface and/or the like). The basestation 5 is also connected to the core network nodes via an appropriateinterface (such as the so-called ‘S1’, ‘N1’, ‘N2’, ‘N3’ interface,and/or the like).

The core network 7 typically includes logical nodes (or ‘functions’) forsupporting communication in the telecommunication system 1. Typically,for example, the core network 7 of a ‘Next Generation’/5G system willinclude, amongst other functions, control plane functions (CPFs) 10 anduser plane functions (UPFs) 11. Such control plane functions (and userplane functions) may provide the functionality of the AMF 710, theUDM/UDR 720, the SMF 730, and/or the NRF 740 discussed in the aboveaspects.

From the core network 7, connection to an external IP network 20 (suchas the Internet) is also provided.

The components of this system 1 are configured to perform the abovedescribed aspects.

User Equipment (UE)

FIG. 10 is a block diagram illustrating, in more detail, the maincomponents of the UE (mobile device 3) shown in FIG. 9 . As shown, theUE 3 includes a transceiver circuit 31 which is operable to transmitsignals to and to receive signals from the connected node(s) via one ormore antenna 33. Although not necessarily shown, the UE will of coursehave all the usual functionality of a conventional mobile device (suchas a user interface 35) and this may be provided by any one or anycombination of hardware, software and firmware, as appropriate. Acontroller 37 controls the operation of the UE in accordance withsoftware stored in a memory 39. The software may be pre-installed in thememory 39 and/or may be downloaded via the telecommunication network 1or from a removable data storage device (RMD), for example. The softwareincludes, among other things, an operating system 41 and acommunications control module 43. The communications control module 43is responsible for handling (generating/sending/receiving) signallingmessages, including uplink/downlink data packets, between the UE 3 andother nodes (e.g., (R)AN nodes 5 and core network nodes), in accordancewith any one of the above described aspects.

(R)AN Node

FIG. 11 is a block diagram illustrating, in more detail, the maincomponents of an exemplary (R)AN node 5 (base station) shown in FIG. 9 .As shown, the (R)AN node 5 includes a transceiver circuit 51 which isoperable to transmit signals to and to receive signals from connectedUE(s) 3 via one or more antenna 53 and to transmit signals to and toreceive signals from other network nodes (either directly or indirectly)via a network interface 55. The network interface 55 typically includesan appropriate base station—base station interface (such as X2/Xn) andan appropriate base station—core network interface (such asS1/N1/N2/N3). A controller 57 controls the operation of the (R)AN node 5in accordance with software stored in a memory 59. The software may bepre-installed in the memory 59 and/or may be downloaded via thetelecommunication network 1 or from a removable data storage device(RMD), for example. The software includes, among other things, anoperating system 61 and a communications control module 63. Thecommunications control module 63 is responsible for handling(generating/sending/receiving) signaling between the (R)AN node 5 andother nodes, such as the UE 3 and the core network nodes/networkelements. Such signaling includes appropriately formatted messages (andinformation elements thereof) in accordance with any one of the abovedescribed aspects.

Core Network Node

FIG. 12 is a block diagram illustrating, in more detail, the maincomponents of a generic core network node (network element or function)shown in FIG. 9 . As shown, the core network node includes a transceivercircuit 71 which is operable to transmit signals to and to receivesignals from other nodes (including the UE 3 and the (R)AN node 5) via anetwork interface 75. A controller 77 controls the operation of the corenetwork node in accordance with software stored in a memory 79. Thesoftware may be pre-installed in the memory 79 and/or may be downloadedvia the telecommunication network 1 or from a removable data storagedevice (RMD), for example. The software includes, among other things, anoperating system 81 and at least a communications control module 83. Thecommunications control module 83 is responsible for handling(generating/sending/receiving) signaling between the core network nodeand other nodes, such as the UE 3, (R)AN node 5, and other core networknodes. Such signaling includes appropriately formatted messages (andinformation elements thereof) in accordance with any one of the abovedescribed aspects.

Modifications and Alternatives

Detailed aspects have been described above. As those skilled in the artwill appreciate, a number of modifications and alternatives can be madeto the above aspects whilst still benefiting from the disclosuresembodied therein. By way of illustration only a number of thesealternatives and modifications will now be described.

In the above description, the UE, the (R)AN node, and the core networknode are described for ease of understanding as having a number ofdiscrete modules (such as the communication control modules). Whilstthese modules may be provided in this way for certain applications, forexample where an existing system has been modified to implement thedisclosure, in other applications, for example in systems designed withthe inventive features in mind from the outset, these modules may bebuilt into the overall operating system or code and so these modules maynot be discernible as discrete entities. These modules may also beimplemented in software, hardware, firmware or a mix of these.

Each controller may comprise any suitable form of processing circuitryincluding (but not limited to), for example: one or more hardwareimplemented computer processors; microprocessors; central processingunits (CPUs); arithmetic logic units (ALUs); input/output (TO) circuits;internal memories/caches (program and/or data); processing registers;communication buses (e.g., control, data and/or address buses); directmemory access (DMA) functions; hardware or software implementedcounters, pointers and/or timers; and/or the like.

In the above aspects, a number of software modules were described. Asthose skilled in the art will appreciate, the software modules may beprovided in compiled or un-compiled form and may be supplied to the UE,the (R)AN node, and the core network node as a signal over a computernetwork, or on a recording medium. Further, the functionality performedby part or all of this software may be performed using one or morededicated hardware circuits. However, the use of software modules ispreferred as it facilitates the updating of the UE, the (R)AN node, andthe core network node in order to update their functionalities.

The above aspects are also applicable to ‘non-mobile’ or generallystationary user equipment.

Various other modifications will be apparent to those skilled in the artand will not be described in further detail here.

CITATION LIST Non Patent Literature

-   [NPL 1] 3GPP TR 21.905: “Vocabulary for 3GPP Specifications”,    V15.0.0 (2018-03)-   [NPL 2] 3GPP TS 23.501: “System Architecture for the 5G System;    Stage 2”, V15.3.0    (2018-9)—http://www.3gpp.org/ftp/Specs/archive/23_series/23.501/23501-f30.zip-   [NPL 3] 3GPP TS 23.502: “Procedures for the 5G System; Stage 2”,    V15.3.0    (2018-9)—http://www.3gpp.org/ftp/Specs/archive/23_series/23.502/23502-f30.zip-   [NPL 4] 3GPP TS 38.413 “NG Application Protocol (NGAP)”, V15.1.0    http://www.3gpp.org/ftp/Specs/archive/38_series/38.413/38413-f10.zip-   [NPL 5] 3GPP TS 38.331 “Radio Resource Control (RRC); Protocol    specification”, V15.3.0    http://www.3gpp.org/ftp/Specs/archive/38_series/38.331/38331-f30.zip-   [NPL 6] 3GPP TR 23.725 “Study on enhancement of Ultra-Reliable    Low-Latency Communication (URLLC) support in the 5G Core network    (5GC”, V2.0.0    http://www.3gpp.org/ftp/Specs/archive/23_series/23.725/23725-200.zip-   [NPL 7] S2-1811754    http://www.3gpp.org/ftp/tsg_sa/WG2Arch/TSGS2_129BIS_WestPalm_Beach/Docs/S2-1811754.zip-   [NPL 8] IEEE 802.1CB-2017: IEEE Standard for Local and metropolitan    area networks—Frame Replication and Elimination for Reliability,    https://ieeexplore.ieee.org/document/8091139/-   [NPL 9] IEEE 802.1Q: “IEEE Standard for Local and metropolitan area    networks—Bridges and Bridged Networks”.

Abbreviations

-   -   5GC 5G Core Network    -   5GS 5G System    -   5G-AN 5G Access Network    -   AMF Access and Mobility Management Function    -   AN Access Network    -   AS Access Stratum    -   DC Dual Connectivity    -   DN Data Network    -   DNN Data Network Name    -   FQDN Fully Qualified Domain Name    -   FRER Frame Replication and Elimination for Reliability    -   GCF Global Certification Forum    -   MNG-RAN Master Next Generation Radio Access Network    -   NAS Non-Access Stratum    -   NEF Network Exposure Function    -   NF Network Function    -   NG-RAN Next Generation Radio Access Network    -   NR New Radio    -   NRF Network Repository Function    -   PDU Protocol Data Unit    -   PLMN Public land mobile network    -   QoS Quality of Service    -   (R)AN (Radio) Access Network    -   RRC Radio Resource Control    -   SD Slice Differentiator    -   SNG-RAN Slave Next Generation Radio Access Network    -   SMF Session Management Function    -   S-NSSAI Single Network Slice Selection Assistance Information    -   SST Slice/Service Type    -   TSN Time Sensitive Networking    -   UDR Unified Data Repository    -   UPF User Plane Function    -   URLLC Ultra Reliable Low Latency Communication    -   VPLMN Visited Public land mobile network

Definitions

For the purposes of the present document, the terms and definitionsgiven in 3GPP TR 21.905 [1] and the following apply. A term defined inthe present document takes precedence over the definition of the sameterm, if any, in 3GPP TR 21.905 [1].

Although the present disclosure has been described above with referenceto some aspects, the present disclosure is not limited to the aspects.The configurations and details of the present disclosure can be changedin various manners that can be understood by one skilled in the artwithin the scope of the present disclosure.

This application is based upon and claims the benefit of priority fromEuropean patent application No. 19150842.3, filed on Jan. 8, 2019, thedisclosure of which is incorporated herein in its entirely by reference.

REFERENCE SIGNS LIST

-   -   1 telecommunication system    -   3 UE    -   31 transceiver circuit    -   33 antenna    -   35 user interface    -   37 controller    -   39 memory    -   41 operating system    -   43 communications control module    -   5 NG-RAN node    -   51 transceiver circuit    -   53 antenna    -   55 network interface    -   57 controller    -   59 memory    -   61 operating system    -   63 communications control module    -   501 NG-RAN node1    -   502 NG-RAN node2    -   7 core network    -   71 transceiver circuit    -   75 network interface    -   77 controller    -   79 memory    -   81 operating system    -   83 communications control module    -   710 AMF    -   720 UDM/UDR    -   730 SMF    -   731 SMF1    -   732 SMF2    -   740 NRF    -   750 UPF    -   751 UPF1    -   752 UPF2    -   10 CPF    -   11 UPF    -   20 external IP network

What is claimed is:
 1. A core network node comprising: a memory storinginstructions; and at least one processor configured to process theinstructions to: receive a request for establishment of a Protocol DataUnit (PDU) session initiated from a User Equipment (UE) for redundanthandling of Ultra Reliable and Low Latency Communication (URLLC), andreject the establishment of the PDU session in response to the corenetwork node determining that the redundant handling is not allowed forthe PDU session using subscription information from a Unified DataManagement (UDM) node.
 2. The core network node according to claim 1,wherein the redundant handling uses Dual Connectivity.
 3. A method for acore network node, the method comprising: receiving a request forestablishment of a Protocol Data Unit (PDU) session initiated from aUser Equipment (UE) for redundant handling of Ultra Reliable and LowLatency Communication (URLLC), and rejecting the establishment of thePDU session in response to the core network node determining that theredundant handling is not allowed for the PDU session using subscriptioninformation from a Unified Data Management (UDM).
 4. The methodaccording to claim 3, wherein the redundant handling uses DualConnectivity.
 5. A User Equipment (UE), comprising: a memory storinginstructions; and at least one processor configured to process theinstructions to: initiate establishment of a Protocol Data Unit (PDU)session for redundant handling of Ultra Reliable and Low LatencyCommunication (URLLC), wherein the establishment of the PDU session isrejected by a core network node in response to the core network nodedetermining that the redundant handling is not allowed for the PDUsession using subscription information from a Unified Data Management(UDM) node.
 6. A method of a User Equipment (UE), the method comprising:initiating establishment of a Protocol Data Unit (PDU) session forredundant handling of Ultra Reliable and Low Latency Communication(URLLC), wherein the establishment of the PDU session is rejected by acore network node in response to the core network node determining thatthe redundant handling is not allowed for the PDU session usingsubscription information from a Unified Data Management (UDM) node.